What's the Best hardware/configuration to stream with wirecast with an i5 iMac?

Hello,
I am setting up a desktop streaming station and want to be able to input/switch multiple HD cameras during the streaming. I am wondering what is the best video mixer/encoder or hardware solution going into a new iMac using the thunderbolt interface? - which blackmagic design product or other product is best? - Looks like the atem television studio switcher might be best? - let it do the switching of cameras and encoding/processing pre computer - so the imac processors don't have to? If this is then going into the thunderbolt imac connection, will wirecast or Ustream's own software; Pro producer or studio producer be able to see this h264 signal on the iMac? Then stream it? Can you also add another wireless camera in to the iMac using Teredek's Cube hardware thru wifi or cellular card? - Has anyone done this with wirecast or Ustreams own software switcher - multicam - pro producer or studio producer?
Thanks,
Mike

Thanks - I'll check out those other companies too!
I'm posting here because this is unbiased and I'm thinking there is such a variety of people from different backgrounds on this forum that may be experimenting with many different software/hardware live streaming configurations. Then hearing which ended up working the best and also from a cost standpoint - but more important than cost, I want it to hold up during a live streaming event and look the best handling HD on certain devices that can handle it or have the available bandwidth.

If using ATEM you'd want to take the uncompressed out SDI/HDMI into iMac using a device like Blackmagic Ultrastudio MiniRecoder. Wirecast and Ustream Producer would not see H.264 source, nor in most cases would you chose a compressed sources vs an uncompressed source if you're going to be live encoding for live streaming.

Keep in mind that ATEM needs matching settings from all cameras as I understand it. In other words all would have to be 1080i59.94 for example.

You may also need another computer to control the ATEM switching.

There's a huge number of Wirecast users with ATEM TVS . Many use rMBP for on location live streaming.

Teradek Cube would work but there would be a latency compared to the hard wired cameras.

You could get a Decklink Quad card in a PCIe to Thunderbolt chassis such as by Sonnett but that would use the iMac CPU to decode all the sources.